Such actuators serve to operate exhaust gas return valves to control the amount of exhaust gas returned to the combustion chamber or secondary air valves to control the amount of secondary air introduced into the exhaust gas piping, which are used to reduce pollutants in internal combustion engines. These actuators are frequently operated electromagnetically, but can also be operated by an electric motor.
An electromagnetically operated secondary air valve is described, for example, in DE 10 2009 058 930 A1. This valve controls, via a globe valve whose valve rod is connected with the armature of the electromagnet, an amount of air to be supplied to the exhaust gas pipe and pumped by a secondary air pump by adjusting, via operation of the electromagnet, a flow cross-section between a fluid inlet duct and a fluid outlet duct connected with the exhaust gas pipe. The valve comprises a non-return flap which, when the valve is closed, is pressed against the valve seat to prevent air from flowing back when exhaust gas pulsations occur. However, air pulsations also act upon the interior of the actuator. Pressure differences also occur in the armature space due to the movement of the armature.
Exhaust gas pulsations occurring in exhaust gas return valves act directly upon the interior of the actuator so that malfunctioning must be expected.
To provide aeration of the armature space and at the same time prevent dirt, in particular spray water, from entering the interior of the electromagnet from outside, DE 10 2008 004 531 B3 describes connecting the armature space with the exterior of the valve via a de-aeration bore. A mushroom valve having an elastic edge bears upon and closes the de-aeration bore when the pressure in the armature space is lower than that of the exterior. The valve opens upon reversal of the pressure difference. This means, however, that aeration is not possible if a vacuum occurs in the armature space. Opening and closing noises are also produced by the movement of the mushroom valve.